1. Technical Field of the Invention
The invention generally relates to arrangements for facilitating assembly, service and maintenance of image-changing signboards. More particularly, the invention relates to an image-changing signboard of the kind comprising an upper and a lower horizontal frame member having a substantially U-shaped cross-section with two opposite legs and a web interconnecting the legs; two opposite, vertical side frame members connecting the horizontal frame members; a plurality of vertical bar-shaped display elements having a triangular cross-section and rotatably mounted in the upper and lower frame members; individual gear units mounted in one of the horizontal frame members for rotating a respective display element, each of said gear units comprising a drive wheel having at least one claw for intermittently engaging a driven, triangular gear wheel connected to a respective display element; and a drive motor connected to a common drive shaft for simultaneously rotating the respective drive wheels of the gear units.
2. Related Art
A previously known signboard of the kind mentioned above (EP 0 261 089 B1) comprises upper and lower horizontal frame members of aluminum, each of which having a U-shaped cross-section profile. The U-profile frame members are located such that one leg of the U is forming a bottom wall, whereas the opposite leg is forming a top wall of the frame member. The web portion connecting the legs of the U-profile is forming a rear wall of the frame member. Drive gear units of the rotatable display bars of the signboard are fixedly mounted in one of the horizontal frame members, usually the upper one. A cover plate is mounted on the front side of the U-shaped frame members. The gear units for the display members are individually mounted to fixed lower and rear walls of the U-profile which requires hole drilling operations in the profile and makes it difficult and cumbersome to carry out service and maintenance works on the signboard, such as demounting the drive gear units for replacement of components, as well as assembly of signboards of various dimensions.